How can nutritional additives modify ruminant nutrition?

This review illustrates the relationships between additives in the diets of ruminants and the consequence for ruminant nutrition. Feed additives are used to improve animal performance and/or the quality of the products. There are several categories of additives available for ruminant nutrition, with emphasis on antibiotics, prebiotics, probiotics, plant extracts, and exogenous enzymes. Antibiotics, essential oils, and chitosan act by selecting sensitive bacteria, consequently modulating the ruminal fermentation pattern. Prebiotics favor microbial growth, providing greater digestion and the production of volatile fatty acids. Probiotics are living microorganisms that improve the ruminal environment, promoting microbial growth and resulting in increased digestion and the production of volatile fatty acids. Exogenous enzymes act synergistically with the enzymes secreted by the ruminal microorganisms, besides favoring microbial adhesion and colonization and facilitating feed degradation. Tannins, whether altering the fermentation standard and/or modifying the ruminal microbiota population, are effective in improving animal performance. However, the effects of additives on the quality of the products are linked to diet quality. Highlights • Exogenous enzymes act synergistically with the enzymes secreted by the ruminal microorganisms. • Exogenous enzymes favoring the microbial adhesion and colonization of the particles, aid in the degradation of the feed. • Tannins can altering the fermentation standard and/or modifying the ruminal microbiota population. • Essential oils and chitosan act by selecting sensitive bacteria and consequently modulate the ruminal fermentation.